Security substrates

Abstract

The security substrate includes an at least partially light transmitting carrier supporting a security feature and includes at least first and second layers, at least one of which covers an area which is less than a full surface area of the carrier and which at least partially overlaps the other layer. The layers have substantially the same color and texture, and the reflective contrast ratio of the overlapping areas and the non-over lapping areas is less than 20 % and the transmissive contrast ratio of the overlapping areas and the non-overlapping areas is greater than 3 %.

The invention claimed is: 
     
       1. A security substrate, said substrate comprising:
 an at least partially light transmitting carrier supporting a security feature, said security feature comprising a first and a second layer and a metallic and a demetallised region at least partially superimposed with the first and second layers, at least one of said first and second layers covering an area which is less than a full surface area of the carrier and which at least partially overlaps the other layer, wherein the first and second layers have substantially the same colour and texture, and the reflective contrast ratio (expressed as a percentage) of the overlapping areas and the non-overlapping areas is less than 20% and the transmissive contrast ratio (expressed as a percentage) of the overlapping areas and the non-overlapping areas is greater than 3%, the contrast ratios of each of the areas defined by the first and second layers being selected in combination with one another such that; 
 when the security substrate is viewed in reflected light, the first and second layers are indiscernible from each other and have the appearance of a single homogenous area; and 
 when the substrate is viewed in transmitted light, the first and second layers are clearly distinguishable from each other. 
 
     
     
       2. A security substrate as claimed in  claim 1  in which the carrier is transparent. 
     
     
       3. A security substrate as claimed in  claim 1  in which at least one of the layers is in the form of an image or indicia. 
     
     
       4. A security substrate as claimed in  claim 1  in which at least one of the layers covers one surface of the carrier. 
     
     
       5. A security substrate as claimed in  claim 1  in which each of said layers is in the form of an image or indicia. 
     
     
       6. A security substrate as claimed in  claim 1  in which the layers are applied to the same surface of the carrier, one at least partially overlying the other. 
     
     
       7. A security substrate as claimed in  claim 1  in which the layers are applied to opposing surfaces of the carrier. 
     
     
       8. A security substrate as claimed in  claim 1  in which one of said layers lies wholly within the boundaries of the other of said layers. 
     
     
       9. A security substrate as claimed in  claim 1  in which the layers are printed. 
     
     
       10. A security substrate as claimed in  claim 9  in which the layers are printed with the same ink. 
     
     
       11. A security substrate as claimed in  claim 9  in which the layers are printed with different inks. 
     
     
       12. A security substrate as claimed in  claim 9  in which the layers are printed with optically variable inks or inks comprising an optically variable pigment or a magnetic optically variable pigment. 
     
     
       13. A security substrate as claimed in  claim 12  in which the layers are printed with a mixture of optically variable pigments and coloured pigments. 
     
     
       14. A security substrate as claimed in  claim 9  in which the layers are printed with metallic inks. 
     
     
       15. A security substrate as claimed in  claim 9  in which the layers are printed with reflective inks. 
     
     
       16. A security substrate as claimed in  claim 1  in which at least one of the layers comprise a pigment dispersed throughout a light transmitting film, which is applied to the carrier. 
     
     
       17. A security substrate as claimed in  claim 1  in which the reflective contrast ratio (expressed as a percentage) is less than 10%. 
     
     
       18. A security substrate as claimed in  claim 1  in which the transmissive contrast ratio (expressed as a percentage) is greater than 5%. 
     
     
       19. A security substrate as claimed in  claim 1  in which the carrier is a paper substrate. 
     
     
       20. A security substrate as claimed in  claim 1  in which the carrier is a plastic substrate. 
     
     
       21. A security article incorporating a security substrate as claimed in  claim 1 . 
     
     
       22. A security article as claimed in  claim 21  in which the security substrate is applied to a surface of the security article in the form of a patch, foil, stripe or the like. 
     
     
       23. A security article as claimed in  claim 21  in which the security substrate is at least partially embedded in the security article and exposed in at least one window therein. 
     
     
       24. A security article as claimed in  claim 21  comprising a banknote, passport, certificate or other document of value.